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Re: need some help on the distillation

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  • Harry
    ... reflux still. ... stripping run I could get the distillate down to about 65% then shut down the run or whenever I chose to shutdown. ... then only gets
    Message 1 of 3 , May 14 1:40 PM
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      --- In new_distillers@yahoogroups.com, "gramssr" <lacrossestanley@...> wrote:
      >
      > I need some help when distilling an Uncle Jessie recipe. I'm using a reflux still.
      >
      > Its been awhile since I've distilled but a few years ago while doing a stripping run I could get the distillate down to about 65% then shut down the run or whenever I chose to shutdown.
      >
      > Now, while doing a stripping run the distillate comes out at 90% but then only gets down to about 83% before the temp at the head is around 205 F and any thing coming out of the pipe starts turning cloudy, the same color as the low wines that I dump into the boiler.
      >
      > The boiler is heated by an electric coil and hasn't been changed, I only dump five gallons into the boiler (the size of the boiler) but I'm thinking maybe dumping in only 4 1/2 gallons? because it could be too full? I'm stripping the run when its around 15-16%. The product going into the boiler is cloudy but any chunks of corn are filtered out.
      >
      > Another thought is reversing the flow of the cooling water, it now goes in at the top of the column but maybe connect the cooling water to the bottom of the coil, closest to the boiler? I think I recall reading that somewhere.
      >
      > I plan on doing another stripping run today and I waited a bit long to request help but any suggestions are certainly appreciated at any time.
      >
      > Stan
      >

       

      Yes I think most of you problem is right there.  Coils should always be fed from the lowest point to allow gravity to work for you in completely filling the coil.  Air pockets can occur if fed the other way, which means the coil is not extracting heat for its full length.  Thus you get temp fluctuations and problems.

      There are many reasons why condensers become poor at heat transfer.  Air pockets are a big one.  Scale or fouling from hard or limestone water feed is another.

      Air pockets are the bane of condensers.  They can occur even in correctly fed condensers due to dissolved air separating out of the water feed during long runs (it always does).  The tiny air bubbles accumulate at the highest point in your condenser and form a 'pocket' where no heat exchange takes place.  Thus the condenser becomes inefficient.  I see this often in liebig condensers where the top water outlet is cut into the shell at a point somewhat below the very top of the shell.  Here's where good design & a bit of forethought will save lots of problems further on.

      Calcium scale fouling will form a physical barrier to heat transfer, even in thin film fouling.  So keep those condenser tubes CLEAN!!!

       

      Slainte!
      regards Harry
      [Groups Owner]

    • gramssr
      ... Thank You! I needed to start the run so I changed the inlet and outlet cooling water then read your reply, your confirmation gave me the confidence I
      Message 2 of 3 , May 14 4:42 PM
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        >
        > Yes I think most of you problem is right there. Coils should always be
        > fed from the lowest point to allow gravity to work for you in completely
        > filling the coil. Air pockets can occur if fed the other way, which
        > means the coil is not extracting heat for its full length. Thus you get
        > temp fluctuations and problems.
        >
        > There are many reasons why condensers become poor at heat transfer. Air
        > pockets are a big one. Scale or fouling from hard or limestone water
        > feed is another.
        >
        > Air pockets are the bane of condensers. They can occur even in
        > correctly fed condensers due to dissolved air separating out of the
        > water feed during long runs (it always does). The tiny air bubbles
        > accumulate at the highest point in your condenser and form a 'pocket'
        > where no heat exchange takes place. Thus the condenser becomes
        > inefficient. I see this often in liebig condensers where the top water
        > outlet is cut into the shell at a point somewhat below the very top of
        > the shell. Here's where good design & a bit of forethought will save
        > lots of problems further on.
        >
        > Calcium scale fouling will form a physical barrier to heat transfer,
        > even in thin film fouling. So keep those condenser tubes CLEAN!!!
        >
        >
        >
        > Slainte!
        > regards Harry
        > [Groups Owner]
        >


        Thank You! I needed to start the run so I changed the inlet and outlet cooling water then read your reply, your confirmation gave me the confidence I needed to continue. I bet when I replaced the plastic water tubing with new stuff in my last move to this apartment I screwed up the orientation.

        I really appreciate your explanation of what can happen, for some reason it makes sense to me to have the coldest cooling water at the top of the column so I thought what I had was correct but like my ex-wife said to me "...I'm full of BS...".

        In your mention of calcium scale fouling, it seems the inside and outside of the copper tubing should be cleaned with vinegar shot through occasionally, is that correct?

        Anyway, the run went well with the correct flow of cooling water, nice to have things back to where they should be and the product is good, I now have a little over two gallons with a gallon of feints (from previous runs) to add back to this finishing run.

        Stan
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